Genome Architecture in Human Germinal Center B Cell Development, Malignancy, and Somatic Hypermutation

总结 在体液免疫应答过程中，体细胞超突变（SHM）引入点突变， 活化的生发中心（GC）B细胞的重排的免疫球蛋白（IG）基因。SHM是必不可少的， 抗体亲和力的微调，表达高亲和力抗体的B细胞的产生，以及 许多疫苗。错误的SHM活动可导致突变和染色体易位， 有助于B细胞淋巴瘤的发展。最近的研究表明，三维（3D） 基因组的组织调节SHM靶向和错误靶向。然而，在很大程度上， 基因组在GC B细胞发育和淋巴瘤中在空间上跨越多个长度尺度组织， 以及3D基因组结构如何机械地影响SHM的靶向和错误靶向。 常规方法不能解决原发性GC组织环境中的这些问题， 技术限制。在这里，我们建议应用我们团队最近开发的一种新方法，称为 对原代人扁桃体组织样品进行核组结构的多重成像（MINA）， 恶性GC衍生的人B细胞淋巴瘤。我们将调查和测试SHM之间的关联 易感性和各种3D核组结构，包括拓扑相关结构域（Topologically Associated Domain，简称NDT） 结构、相分离和基因组区域相对于核纤层的核定位， 核仁和核孔。通过靶向人类B细胞淋巴瘤的基因组扰动，我们将 测试将SHM靶向元件与升高的染色质循环相互作用联系起来的特定假设， 相分离、核孔接近和突变脆弱性。我们的研究将大大促进我们的 了解3D基因组结构和核组织在GC B细胞中的作用 SHM在发育和肿瘤发生背景下。我们希望这项研究能够建立一个新的 研究范式和转换免疫生物学中的3D核组研究。

SUMMARY During the humoral immune response, somatic hypermutation (SHM) introduces point mutations in rearranged immunoglobulin (Ig) genes of activated germinal center (GC) B cells. SHM is essential for the fine-tuning of antibody affinity, the generation of B cells expressing high-affinity antibody, and the efficacy of many vaccines. Mistargeted SHM activities can lead to mutations and chromosomal translocations that contribute to the development of B cell lymphoma. Recent studies suggest that the three-dimensional (3D) organization of the genome regulates SHM targeting and mistargeting. However, it is largely unknown how the genome is spatially organized across multiple length scales in GC B cell development and lymphoma, and how 3D genome architecture mechanistically affects the targeting and mistargeting of SHM. Conventional approaches cannot address these questions in the primary GC tissue environment due to technical limitations. Here, we propose to apply a new method recently developed by our team, termed Multiplexed Imaging of Nucleome Architectures (MINA), to primary human tonsil tissue samples and malignant GC-derived human B cell lymphomas. We will investigate and test the association between SHM susceptibility and a variety of 3D nucleome architectures, including topologically associating domain (TAD) architecture, phase separation, and nuclear positioning of genomic regions relative to nuclear lamina, nucleoli, and nuclear pores. Through targeted genomic perturbations in human B cell lymphomas, we will test specific hypotheses linking SHM targeting elements to elevated chromatin looping interactions, TAD phase separation, nuclear pore proximity, and mutation vulnerability. Our study will significantly advance our understanding of the role of 3D genome architecture and nuclear organization in GC B cells undergoing SHM in both the developmental and tumorigenesis contexts. We expect this study to establish a new research paradigm and transform 3D nucleome investigations in immunobiology.